Instruments which rely upon regulated fluid flow are commonly employed in a wide variety of applications, such as sample purification, chemical analysis, clinical assay, and industrial processing. For many instruments, an extensive and complex array of tubular devices in the form of tubing, fittings, connectors, and the like are employed to provide the many flow paths that are necessary for optimum operation, and to effect the attachment of other devices such as sensors, valves, and the like.
Very often, such instruments devices require a complex arrangement of devices in a flow system having multiple flow paths. Generally, efficient operation of a flow system requires a combination of flow-through components, such as valves, sensors, columns, and connective tubing, with terminal components, such as needles, pumps, and drains. Different flow paths are frequently required to, for example, isolate a component from the flow system, include a component into the flow system, or rearrange the order of the components in the flow system. Further, there is the need to sense certain characteristics of the fluid flow at differing points in the flow paths. Examples of such sensed characteristics include the pressure, flow rate, and temperature of the fluid. Other characteristics related to the particular fluid flow include the presence or absence of a fluid component, such as an analyte or contaminant. Such needs are typically addressed by the use of fluid connectors for attachment of differing devices. Combinations of fluid connectors are sometimes necessary to provide flow paths among the flow-through components and terminal components employed in a flow system.
There exists the practical problem, therefore, of connecting an array of tubular devices that are required for the multitude of flow path combinations in a modern instrument. Another practical problem remains in connecting quite a large number of devices in a multitude of flow path combinations in a confined spaced within an instrument. The complexity of such systems also introduces reliability concerns. Because the instruments having these flow systems are sometimes mass-produced for automated or unattended operation, the cost and reliability of the fluid connection are features critical to successful operation of the instrument.
Another problem involves the proper orientation of all of the tubing, valves, sensors, and the like so as to allow the designer to achieve the desired combinations of flow paths, yet also provide an assembly that is compact, easily-manufactured, inexpensive, and reliable. The provision of fluid-tight connections in a complex fluid-handling assembly has become exceedingly problematic as the assembly is reduced in size.
In response to these problems, U.S. Pat. No. 5,567,868, issued to Craig et al., disclosed an instrument, preferably in the form of a chromatograph, that includes a computer, a pneumatic controller responsive to the computer, and planar manifold assembly. The planar manifold assembly includes one or more fluid-handling functional devices attached to a planar manifold. Multiple fluid-handling functional devices may then be coordinated and assembled so as to connect to pneumatic channels that are integrated in the planar manifold, and thus many of the fluid flow paths are integral to the planar manifold, which is itself quite compact and amenable to construction in a variety of shapes and configurations. The advantages of the planar manifold assembly include the reduction of external connections between fluid-handling functional devices (such as fittings, valves, sensors, and the like) by use of a single planar manifold for the provision of a plurality of flow paths. The fluid-handling functional devices that connect to the planar manifold are constructed to be surface-mounted to offer reliable, fluid-tight connection without the complexity and difficulty of previously-known pneumatic connections.
Nonetheless, there still remains a difficulty in effecting such simple, reliable, and inexpensive fluid connections between a tubular device and a port situated in a planar surface on a planar device. Such planar surfaces may be found on a machined part designed for use with the planar manifold assembly, such as a microminiature valve, or, in particular, on the above-described planar manifold. Conventional fluid connectors have several significant disadvantages that make them unsuitable for this task. Firstly, they require some type of fitting to be machined, brazed, or otherwise attached to the port, thus requiring a substantial fabrication cost and effort; secondly, they typically exhibit a dead space communicating with the ends of the fluid channels being coupled. A portion of the fluid emerging from the end of one channel quickly finds its way into the dead space but a relatively long time is required for it to enter the other channel. For example, in a tube connected by conventional compression fitting connector to a receiving fitting on a detector in a chromatograph, the concentration of a sample fluid emerging from one end of the tube must increase rapidly to a maximum value and then rapidly decay to zero to be detected as a chromatographic peak. When this high concentration enters the unswept dead space, it only leaves by diffusion which, as it is slow, causes the concentration peak to decay slowly . This undesirable phenomenon is known as tailing. As those skilled in the art are aware, such a phenomenon can make it difficult to detect separate components of the sample. Another significant disadvantage of conventional fluid connectors is that the fluid flowing through the fluid connector can be degraded by contact with large areas of less-than-inert surfaces of the device. Still another significant disadvantage of conventional fluid connectors is that planar fluid handling devices, such as the planar manifold assembly described hereinabove, are becoming even smaller and are designed to be assembled to form a compact, densely-populated arrangement of parts. Conventional fluid connectors, in contrast, remain undesirably large and bulky.
There is accordingly a need in many applications for a fluid connector system for use in effecting a fluid connection between a tubular device and a port on a planar surface in a planar device, wherein such a system would offer such attributes as: miniaturization, reliability, simplicity, robustness, ease in assembly and maintenance, and low cost.